This invention relates to orthognathic set-ups and more particularly to an apparatus and method for providing a plane of reference with respect to an arch model mounted in dental surgical instruments, such as an articulator.
Orthognathic dental surgery has achieved remarkable success with may patients. In this type of surgery, the position of one or both of the jaws of a patient are surgically altered. Although sometimes quite complicated and painful for a patient undergoing this surgery, the results achieved have been enormously beneficial both in its functional and in its aesthetic effects. Patients who formerly had gross malocclusions which distorted their appearance and made even the simple act of chewing food a chore have achieved a normal appearance and normal chewing process through dental surgery.
A number of techniques have been used in dental surgery to determine the extent to which the maxillary (upper jaw) and/or the mandible (lower jaw) need to be surgically adjusted in order to correct an existing malocclusion. The most accurate method currently known in the art involves the following technique. First, maxillary and mandibular arch models (dental casts) of the patient are made. Vertical and horizontal lines are then drawn on each model in a predetermined fashion so as to serve as reference points. After the arch models are mounted on an articulator so as to simulate and duplicate as accurately as possible the patient's malocclusion, position adjustments are made by cutting out wedges of material in an arch model (or models) and then seeing how the modified position improves occlusion and aesthetic appearance. The remaining arch model lines provide a rough indication of the extent of position modification performed.
It is a tedious and time consuming job to mark the arch models. Additionally, the lines are drawn by hand and are therefore inherently inaccurate. This becomes of critical importance when the dental surgeon attempts to reproduce the adjustments in the patient's mouth during surgery. Furthermore, when position adjustments are made, they almost always have an effect on more than just one plane. For instance, if a wedge or cut is made to shorten the jaw along the x axis, i.e., to adjust the jaw in the x direction, it will almost invariably affect the plane of occlusion along the y & z axes as well. It has been found to be very difficult to judge these effects using the above-described technique.
Consequently, there is a need to provide methods and devices which will enable more accurate determination of the position modification created in an arch model so as to enable its accurate implementation in a patient's mouth during surgery and to provide this function in a simple and easy to use way.